The public cost of refurbishing the Kensington Palace apartment that will be the new home of the Duke and Duchess of Cambridge and their baby is £1m, the Queen's accounts reveal.

Once home to Princess Margaret until she died in 2002, Apartment 1A – a 21-room abode over four storeys – has since been used as office and storage space.

Much of the cost - £600,000 - is to remove asbestos. A further £400,000 has been spent on repairing and renewing the roof.

Kensington Palace will be the Duke and Duchess of Cambridge's new home after a £1m refit. Photograph: Martin Keene/PA

The "aunt heap", as the Duke of Windsor – formerly Edward VIII – referred to it in a nod to its reputation as the home for hard-up royal relations, became a palace when William of Orange bought it in 1689, and was improved and extended by Sir Christopher Wren.

Apartment 1A needed some significant redecoration, the cost of which will be met privately. At one stage Margaret and her husband Lord Snowdon jazzed it up with an of-its-time pink, turquoise and orange colour scheme. It has since been gutted and is being completely refitted. Its 21 rooms include a drawing room, staff quarters and a nursery.

Royal travel costs

William and Kate visited the Kranji Memorial Cemetery in Singapore on September 13, 2012. The flights for their tour cost £370,590. Photograph: Nicolas Asfouri/AFP/Getty Images

The Duke and Duchess of Cambridge's colourful Singapore and south Pacific tour set the taxpayer back £370,590 in travel costs, including the price of a reconnaissance trip by royal staff.

Prince Charles racked up a £235,325 travel bill for charter flights on an eight-day Middle-East tour. He was also the highest spender on the royal train – notorious for being the most expensive form of royal travel per mile. A two-day trip from Ayr to Liverpool, Stoke-on-Trent, Northampton and Peterborough cost £33,547, and another from Highgrove to Bishop Auckland, Alnmouth and Kings Lynn totalled £34,547.

Princess Anne, regarded as the thriftiest royal, spent £42,176 on a return scheduled flight from Heathrow to Johannesburg for an official jubilee visit. Pressed on why, royal aides said that she, her husband Sir Tim Laurence, a private secretary and a lady-in-waiting had all travelled first class, while her dresser and a "web manager" were in business class.

Prince Andrew flew on a charter to attend the funeral of Crown Prince Nayef bin Abdul-Aziz of Saudi Arabia at a cost of £86,092. It emerged that a government minister had hitched a lift but paid only the cost of a scheduled ticket. "It wasn't a case of saying: 'If you're coming, £43,000 is yours,'" joked an aide.